This invention relates to an improved cleaning means for an electrophotographic copier or a printer and an image-forming process and image-forming apparatus each in which the cleaning means is used.
Heretofore in the electrophotography based on Carlson process, an image is formed in the following manner. A uniform charge is applied to the surface of an image-forming member; an electrostatic latent image is formed by making an imagewise exposure; a toner image is formed by developing the latent image; and the toner image is transferred and fixed to an image transfer member.
After making the image transfer, the image-forming member is cleaned up by a cleaning means and is then used repeatedly for a long time. It is inevitable for the cleaning step to have both of a cleaning function by which toner remaining on an image-forming member is effectively scraped away by a cleaning means such as a cleaning blade, and a toner collecting function by which cleaned up toner is smoothly collected on the outside of an image-forming region by a collecting means such as a cleaning roller. When the two functions are fulfilled satisfactory, an excellent cleaning operation can be performed.
According to the studies through many years made by the inventors, a toner guide roller is required to satisfy the following peculiar requirements to fully perform the functions.
To be more concrete, it is required to satisfy the following requirements:
(1) A guide roller itself is great in durability, strong in mechanical abrasion resistance and resistant to the functions of activator such as ozone produced by a discharge, because the roller is relatively close to a corona discharge electrode;
(2) When the guide roller is rotated by coupling it to the rotation of an image-forming member, the roller is well followed around the image-forming member without any slipping off of the rotation and any erroneous rotation is not produced even when the roller is forcibly rotated;
(3) Toner scraped off from the image-forming member adheres to the guide roller surface so that the toner can smoothly be transported, and the roller is excellent in toner transportability and in separability of the adhered toner from the roller, because the adhered toner is to be collected smoothly by a scraper;
(4) The guide roller surface has a proper elasticity and is brought into close contact with the surface of the image-forming member without any gap so that the roller can be rotated without producing any toner scattering;
(5) When the guide roller is rotated, the image-forming member surface can neither abraded nor damaged; and
(6) In an image transfer step, the roller is to be efficiency in removal of paper dust.
For the techniques in which toner scraped off from the surface of an image-forming member by a cleaning means such as a cleaning blade and an elastic roller is collected by the above-mentioned elastic roller, there are some proposals therefor such as those disclosed in Japanese Patent Publication Open to Public Inspection (hereinafter referred to as JP OPI Publication) Nos. 60-107675/1985, 61-67073/1986 and 1-267679/1989. Wherein an elastic roller comprising a foamed material such as urethane rubber, chloroprene rubber, silicone rubber and sponge is served as both a cleaning means together with a cleaning blade and a toner guide roller, such elastic roller is rotated by bringing it into pressure contact with an image-forming member so that cleaned up toner scraped off by the cleaning means is made adhered to the guide roller and is then transported by the guide roller to a toner collection unit.
The above-mentioned foamed material such as sponge herein means that it has a pore size of not smaller than 100 .mu.m and it is quite different in itself from the open-cell cellular materials of the invention.
However, the guide rollers described in the above-mentioned patent publications cannot satisfy all the requirements (1) through (6). In the present state where a high-speed operation and a high image quality are recently demanded on copying machines, most of the above-mentioned requirements have not been satisfied and the improvements of the guide roller have also been urgently needed.
For example, Japanese Utility Model Publication Open to Public Inspection No. 57-172470/1982 proposes for an elastic roller having at least the surface comprising an open-cell cellular material to serve as a cleaning means in place of the above-mentioned cleaning blade for a copying machine. Wherein cleaned up toner is collected by a suction fan.
The elastic roller described therein is strictly a cleaning means for an image-forming member and remaining toner is required to be scraped off at a high rotation speed. It is therefore difficult to select a peculiar cellular material to meet the requirement. There are some problems that the size of a cleaning unit becomes remarkably larger than in the other image-forming apparatuses, that a noise is produced and that a cleaning effect becomes more unsatisfactory than in a cleaning blade.
It is an object of the invention to provide a toner guide roller by which toner scraped off by a cleaning blade is made adhered to and then transported to a collection member efficiently and fully.
Another object of the invention is to provide a toner cleaning device, an image-forming process and an image-forming apparatus each in which a toner cleaning property is excellent in a process of repeatedly forming images and, particularly, an image is not deteriorated by the surface of an image-forming member damaged by a toner guide roller so that a high quality image can stably be obtained.